CN211909480U - Converters, HVDC transmission facilities and reactive power compensation facilities - Google Patents

Abstract

The utility model relates to a converter, which has a plurality of modules, and the modules respectively have at least two electronic switching elements and an electric energy storage device. The energy storage device is a liquid cooled energy storage device. The utility model also relates to a high-voltage direct current transmission facility with the converter and a reactive power compensation facility with the converter.

Description

Converters, HVDC transmission facilities and reactive power compensation facilities

technical field

The utility model relates to a converter, which has a plurality of modules, and the modules respectively have at least two electronic switching elements and an electric energy storage device. In addition, the utility model relates to a high-voltage direct current transmission facility with a converter and a reactive power compensation facility with a converter.

Background technique

A converter is a power electronic circuit used to convert electrical energy. By means of a converter it is possible to convert alternating current to direct current, direct current to alternating current, alternating current to alternating current of other frequencies and/or amplitudes or direct current to direct current of other voltages. The converter can have a plurality of modules of the same type described above (which are also referred to as submodules), which are electrically connected in series. Such converters are called modular multilevel converters and belong to the category of VSC converters (VSC=voltage source converter). High output voltages can be achieved by the electrical series circuit of the modules. The converter can be simply matched to different voltages (scalable) and can produce the desired output voltage relatively accurately. Modular multilevel converters are often used in the high voltage range, eg as converters in HVDC transmission installations.

During operation of such a converter, the electrical energy storage device is charged and discharged again with electrical energy. Due to the high currents flowing there, the electrical energy storage device can heat up significantly; a large power loss can occur in the energy storage device and a large amount of heat (waste heat) can be generated. Therefore, relatively large distances must be formed between a plurality of electrical energy storage devices or between the electrical energy storage devices and adjacent components in order to be able to discharge waste heat from the electrical energy storage devices to the surrounding air and to be able to dissipate The waste heat is carried away by means of the surrounding air (passive cooling of the electrical energy storage device by air convection).

Utility model content

The present invention is based on the object of proposing a converter and a method in which the packing density of the electrical energy storage device can be increased.

The object is achieved by a converter, a high-voltage direct current transmission facility and a reactive power compensation facility, the converter having a plurality of modules each having at least two electronic switching elements and an electrical An energy storage device, characterized in that the energy storage device is a liquid-cooled energy storage device, the HVDC transmission facility has the converter, and the reactive power compensation facility has the converter. Advantageous embodiments of the converter and the method are given below.

A converter with a plurality of modules is disclosed, each of which has at least two electronic switching elements and an electrical energy storage device, wherein the energy storage device is a liquid-cooled energy storage device. That is, the energy storage device is cooled by means of liquid cooling. In other words, the energy storage device is cooled by means of a liquid coolant (cooling liquid). The energy storage device can be, for example, a capacitor. It is particularly advantageous here if the energy storage device discharges the heat (waste heat) generated in it to the cooling liquid and not to the surrounding air. Thus, large free spaces or spacings around the energy storage device are not necessary, since the cooling of the energy storage device is not based on convection. The packing density of the energy storage devices in the converter, that is to say the number of energy storage devices per volume unit, can advantageously be increased, that is to say that the energy storage devices can, for example, be installed closely next to one another. With improved cooling, energy storage devices with greater energy density or power density can also be used. The service life of the energy storage device is also increased by better cooling and thus less heating of the energy storage device. Furthermore, the surrounding air of the energy storage device is only slightly heated, so that the outlay for air conditioning the space in which the converter is arranged can be considerably reduced compared to the case of passive air cooling.

The converter can be designed such that the converter has a cooling device with a liquid coolant. As the liquid coolant, for example, deionized water (deionized water) or ethylene glycol can be used.

The converter can be designed such that the energy storage device is thermally coupled to the coolant. The waste heat can be quickly and comprehensively discharged from the energy storage device to the liquid coolant by means of the thermal coupling.

The converter can also be designed such that the energy storage device is thermally coupled to the coolant, wherein the energy storage device is provided with a cooling body (energy storage device cooling body) and the cooling body is thermally coupled to the coolant. In this embodiment, the waste heat is first discharged from the condenser to the cooling body and then from the cooling body to the coolant.

The converter can be designed such that the electronic switching elements are liquid-cooled electronic switching elements. In other words, the electronic switching element can be cooled by means of a liquid coolant (cooling liquid). As a result, the electronic switching element can also advantageously be cooled by means of a liquid coolant.

The converter can also be designed such that the electronic switching element is thermally coupled to the coolant.

In particular, the converter can be designed such that the electronic switching element is thermally coupled to the coolant, wherein the electronic switching element is provided with a cooling body (switching element cooling body) and the cooling body is thermally coupled to the coolant.

The converter can also be designed such that the cooling device has a coolant circuit (circuit of coolant) for cooling the energy storage device. The coolant circuit enables efficient removal of waste heat from the energy storage device.

The converter can also be designed such that the cooling device has a coolant pump and a heat exchanger (heat exchanger).

The converter can be designed such that the electrical energy storage device is a capacitor. In particular, the electrical energy storage device can be a unipolar capacitor, that is to say a capacitor with a predetermined polarity of the two capacitor terminals.

The converter can be designed such that

– the two electronic switching elements of the module are arranged as a half-bridge circuit, or

– the modules each have two of said electronic switching elements and two further electronic switching elements,

The two electronic switching elements and the two other electronic switching elements are configured as a full-bridge circuit.

Here, the two other electronic switching elements can be cooled in the same way as the two electronic switching elements. In the case of the first alternative, such a module is also referred to as a half-bridge module or as a half-bridge submodule. In the case of the second alternative, such a module is also referred to as a full-bridge module or as a full-bridge submodule.

Also disclosed are HVDC transmission installations and reactive power compensation installations with converters according to the aforementioned variants.

Also disclosed is a method for cooling at least one electrical energy storage device of a converter, wherein the converter has a plurality of modules, wherein the modules each have at least two electronic switching elements and an electrical energy storage device, wherein in the method

- Cooling of electrical energy storage devices by means of a liquid coolant.

Preferably, the energy storage device of the plurality of modules can be cooled by means of a liquid coolant.

The method can be carried out in that the electronic switching elements of the respective modules are also cooled by means of a liquid coolant.

The method can be carried out by transporting a liquid coolant to the energy storage device by means of a coolant circuit.

The method can also be carried out by transporting a liquid coolant to the electronic switching element by means of a coolant circuit.

The described converter and the described method have the same or similar advantages.

Description of drawings

Hereinafter, the present utility model will be described in detail according to the embodiments. The same reference numerals denote identical or identically functioning elements here. to this end

An embodiment of a converter is shown in FIG. 1 having a plurality of modules;

One embodiment of a module is shown in Figure 2;

Another embodiment of the module is shown in Figure 3;

One embodiment of a HVDC transmission facility is shown in FIG. 4;

One embodiment of a reactive power compensation facility is shown in FIG. 5; and

An exemplary sequence of a method for cooling an energy storage device of a module of a converter is shown in FIG. 6 .

Detailed ways

A converter 1 in the form of a modular multilevel converter (MMC) is shown in FIG. 1 . The multi-level converter 1 has a first AC voltage terminal 5 , a second AC voltage terminal 7 and a third AC voltage terminal 9 . The first AC voltage terminal 5 is electrically connected to the first phase module branch 11 and the second phase module branch 13 . The first phase module branch 11 and the second phase module branch 13 form the first phase module 15 of the converter 1 . The end of the first phase module branch 11 away from the AC voltage terminal 5 is electrically connected to the first DC voltage terminal 16 ; the end of the second phase module branch 13 away from the first AC voltage terminal 5 is electrically connected to the second DC voltage terminal 17 Electrical connections. The first DC voltage terminal 16 is a positive DC voltage terminal; the second DC voltage terminal 17 is a negative DC voltage terminal.

The second AC voltage terminal 7 is electrically connected to the end of the third phase module branch 18 and to the end of the fourth phase module branch 21 . The third phase module branch 18 and the fourth phase module branch 21 form a second phase module 24. The third AC voltage terminal 9 is electrically connected to the end of the fifth phase module branch 27 and to the end of the sixth phase module branch 29 . The fifth phase module branch 27 and the sixth phase module branch 29 form a third phase module 31 .

The end of the third phase module branch 18 facing away from the second AC voltage terminal 7 and the end of the fifth phase module branch 27 facing away from the third AC voltage terminal 9 are electrically connected to the first DC voltage terminal 16 . The end of the fourth phase module branch 21 facing away from the second AC voltage terminal 7 and the end of the sixth phase module branch 29 facing away from the third AC voltage terminal 9 are electrically connected to the second DC voltage terminal 17 . The first phase module branch 11, the third phase module branch 18 and the fifth phase module branch 27 form the positive side converter part 32; the second phase module branch 13, the fourth phase module branch 21 and the The six-phase module branch 29 forms the negative-side converter part 33 .

Each phase module branch has a plurality of modules (1_1, 1_2, 1_3, 1_4, ..., 1_n; 2_1, ..., 2_n; etc.) which are electrically connected in series (by means of their electrical current terminals) . Such modules are also called submodules. In the embodiment of Figure 1, each phase module branch has n modules. The number of modules electrically connected in series by means of their current terminals can be very different, at least two modules are connected in series, but for example also 3, 50, 100 or more modules can be electrically connected in series. In the embodiment, n=36: that is, the first phase module branch 11 has 36 modules 1_1, 1_2, 1_3, . . . , 1_36. The other phase module branches 13 , 18 , 21 , 27 and 29 are of the same type.

Optical messages or optical signals are transmitted to the individual modules 1_1 to 6_n via an optical communication connection, eg via an optical waveguide, by a control device (not shown) of the converter 1 . For example, the control device respectively transmits to the respective modules the desired value regarding the height of the output voltage, which should be provided by the respective module.

The converter 1 has a cooling device 50 . The cooling device 50 has a coolant container 52, a pump 54 (coolant pump 54), and a heat exchanger 56 (heat exchanger 56). The coolant container 52 , the pump 54 and the heat exchanger 56 are connected via coolant lines 60 to the individual modules 1_1 , . . . , 6_n of the converter 1 . (The coolant line 60 is shown in the exemplary embodiment by means of two parallel lines in the form of pipes.) Thus, for example, the heat exchanger 56 is connected to the module 1_1 via the outgoing coolant line 60a; the module 1_1 is connected via the coolant line 60b is connected to module 1_2; and module 1_2 is connected to module 1_3 via coolant line 60c. In the same manner and method, the module 1_3 is connected with the next module 1_4 (not shown) via coolant lines, and so on. The last module 1_n of the phase module branch 11 is connected to the coolant container 52 via a return cooling line 60d. The coolant container 52 is connected via the coolant line 60 to the pump 54 ; the pump 54 is connected via the coolant line 60 to the heat exchanger 56 .

There is a reserve of coolant 70 in the coolant container 52 . The coolant 70 can be pumped from the coolant container 52 by means of the pump 54 through the heat exchanger 56 , through the modules 1_1 , . . . , 1_n of the first phase module branch 11 and then pumped back to the coolant container again 52. Thus, the cooling device 50 has the coolant circuit 72 . The modules 3_1 , . . . , 3_n of the third phase module branch 18 and the modules 5_1 , . . . , 5_n of the fifth phase module branch 27 are also connected to the coolant circuit 72 . That is to say, the energy storage devices of a plurality of modules and/or the electronic switching elements of a plurality of modules (here modules 1_1 , ..., 1_n, modules 3_1, ..., 3_n of the third phase module branch, and modules 5_1,..., 5_n of the fifth phase module branch 27).

In order to cool the electronic switching elements and/or the energy storage devices of the modules of the second phase module branch 13 , the fourth phase module branch 21 and the sixth phase module branch 29 , a further cooling device 80 is present. The further cooling device 80 is constructed in the same way as the cooling device 50 described above. It goes without saying that in another exemplary embodiment, the converter 1 can also be cooled by means of a single cooling device (that is to say, by means of a single coolant container 52 , a single pump 54 and a single heat exchanger 56 ). of all modules. Alternatively, it is also possible to use more than two cooling devices to cool the modules of the converter 1 .

Coolant container 52 contains a reserve of coolant 70 . The coolant container 52 is optional: coolant can also be present in sufficient quantities in the coolant line 60 , in the pump 54 and in the heat exchanger 56 .

The construction of the module 201 is shown by way of example in FIG. 2 . In this case, it can be, for example, the module 1_1 of the first phase module branch 11 (or also one of the other modules shown in FIG. 1 ). The module is formed as a half-bridge module 201 . The module 201 has a switchable and switchable first electronic switching element 202 (first electronic switching element 202) with a first diode 204 (first freewheeling diode 204) connected in antiparallel. Furthermore, the module 201 has a switchable and switchable second electronic switching element 206 (second electronic switching element 206 ) with a second antiparallel-connected diode 208 (second freewheeling diode 208 ) and a capacitor 210 Energy storage device 210 in the form of electricity. The first electronic switching element 202 and the second electronic switching element 206 are respectively configured as IGBTs (insulated-gate bipolar transistors). The first electronic switching element 202 is electrically connected in series with the second electronic switching element 206 . At the connection point between the two electronic switching elements 202 and 206, a (galvanic) first module terminal 212 is provided. At the terminal of the second switching element 206 opposite the connection point, a second (current) module terminal 215 is provided. The second module terminal 215 is also connected to the first terminal of the energy storage device 210 ; the second terminal of the energy storage device 210 is electrically connected to the terminal of the first switching element 202 opposite the connection point.

That is, the energy storage device 210 is electrically connected in parallel with the series circuit formed by the first switching element 202 and the second switching element 206 . By correspondingly actuating the first switching element 202 and the second switching element 206 , it can be achieved that either the voltage of the energy storage device 210 or no voltage is output between the first module terminal 212 and the second module terminal 215 (that is, the output zero voltage). Accordingly, a corresponding desired output voltage of the converter can be generated by the cooperation of the modules of the individual phase module branches. In the present embodiment, the actuation of the first switching element 202 and the second switching element 206 is carried out by means of messages and signals (mentioned above) transmitted from the control device of the converter to the module.

The first electronic switching element 202 is provided with a first switching element cooling body 220 ; the second electronic switching element 206 is provided with a second switching element cooling body 222 . The first freewheeling diode 204 is provided with a first diode cooling body 226 ; the second freewheeling diode 208 is provided with a second diode cooling body 228 . The energy storage device 210 is provided with an energy storage device cooling body 230 . The cooling bodies 220, 222, 226, 228 and 230 can each consist of solid metal, for example copper or aluminum. The cooling body is only shown schematically in FIG. 2 . The cooling bodies 220 , 222 , 226 , 228 and 230 are in close thermal contact with the respective components and are able to absorb the waste heat generated in the components and conduct them back to the liquid coolant 70 . Accordingly, the cooling bodies 220, 222, 226, 228, and 230 are in intimate thermal contact (thermally coupled) with the coolant 70, respectively. Thus, the energy storage device 210 , the first electronic switching element 202 , the second electronic switching element 206 , the first freewheeling diode 204 and the second freewheeling diode 208 are thermally coupled with the coolant 70 .

In the lower part of FIG. 2 , the coolant 70 flowing into the module 201 is shown by means of arrows 236 ; in the upper part of FIG. 2 , the coolant 70 flowing out of the module 201 is shown by means of arrows 238 . That is, the first electronic switching element 202, the second electronic switching element 206, the first freewheeling diode 204, the second freewheeling diode 208 and the energy storage device 210 can be cooled by means of the coolant 70 flowing through the module 201. Alternatively, it is of course also possible to cool only individual components of the module, for example only the energy storage device 210 , by means of the coolant 70 . In this case, other cooling possibilities can exist for the cooling of the switching elements and the freewheeling diodes, for example an own coolant circuit.

Coolant 70 absorbs waste heat from energy storage device 210 . Furthermore, the coolant 70 absorbs the waste heat of the first electronic switching element 202 , of the second electronic switching element 206 , of the first freewheeling diode 204 and of the second freewheeling diode 208 . Coolant 70 transports the absorbed waste heat to heat exchanger 56. The heat exchanger 56 discharges the waste heat of the coolant to the ambient air (preferably, the heat exchanger 56 discharges the waste heat to the ambient air located outside the converter building). That is, the energy storage device 210 is a liquid cooled energy storage device 210 ; the energy storage device 210 is cooled by means of the liquid coolant 70 . In the same way, the electronic switching elements 202 , 206 are liquid cooled electronic switching elements 202 , 206 .

Another embodiment of a module 301 of a modular multilevel converter is shown in FIG. 3 . Said module 301 can be, for example, module 1_2 (or also one of the other modules shown in FIG. 1 ). In addition to the first electronic switching element 202 , the second electronic switching element 206 , the first freewheeling diode 204 , the second freewheeling diode 208 and the energy storage device 210 already known from FIG. The module 301 has a third electronic switching element 302 with a third freewheeling diode 304 connected in antiparallel and a fourth electronic switching element 306 with an antiparallel connected Fourth freewheeling diode 308 . The third electronic switching element 302 and the fourth electronic switching element 306 are each configured as IGBTs. Unlike the circuit of FIG. 2 , the second module terminal 315 is not electrically connected to the second electronic switching element 206 , but is electrically connected to the midpoint of the electrical series circuit formed by the third electronic switching element 302 and the fourth electronic switching element 306 . connect.

The module 301 of FIG. 3 is a so-called full bridge module 301 . The full-bridge module 301 is characterized in that it can optionally output energy upon corresponding actuation of the four electronic switching elements between the (galvanic) first module terminal 212 and the (galvanic) second module terminal 315 . A positive voltage of the storage device 210, a negative voltage of the energy storage device 210, or a voltage of zero value (zero voltage). Thereby, that is to say, the polarity of the output voltage can be reversed by means of the full-bridge module 301 . The converter 1 can have either only half-bridge modules 201 , only full-bridge modules 301 , or also half-bridge modules 201 and full-bridge modules 301 . A large current flows through the converter via the first module terminals 212 and the second module terminals 215 , 315 .

In this exemplary embodiment of the module 301 , in addition to the energy storage device 210 , the first electronic switching element 202 , the second electronic switching element 206 , the first freewheeling diode 204 and the second freewheeling diode 208 , additionally by means of The coolant 70 of the coolant circuit 72 cools the third electronic switching element 302 , the fourth electronic switching element 306 , the third freewheeling diode 304 and the fourth freewheeling diode 308 .

One embodiment of a HVDC transmission facility 401 is schematically shown in FIG. 4 . The HVDC transmission facility 401 has two converters 1 , as shown in FIG. 1 . The two converters 1 are electrically connected to each other on the DC voltage side via a high voltage DC connection 405 . In this case, the two positive DC voltage terminals 16 of the converter 1 are electrically connected to each other by means of a first high-voltage DC line 405a; the two negative DC voltage terminals 17 of the two converters 1 are electrically connected by means of a second high-voltage DC line 405a The DC lines 405b are electrically connected to each other. Electrical energy can be transmitted remotely by means of such a HVDC transmission facility 401 ; the HVDC connection 405 then has a corresponding length.

One embodiment of a converter 501 is shown in FIG. 5 , which converter is a reactive power compensator 501 . The converter 501 has only three phase module branches 11, 18 and 27, which form the three phase modules of the converter. The number of phase modules corresponds to the number of phases of the AC grid 511 to which the converter 501 is connected.

The three phase modules 11 , 18 and 27 are connected to each other in a delta, that is to say, the three phase modules 11 , 18 and 27 are connected in a delta circuit. Each corner point of the delta circuit is electrically connected to phase lines 515 , 517 and 519 of the three-phase alternating current grid 511 , respectively. (In another embodiment, the three phase modules can also be connected in a star circuit instead of a delta circuit.) The converter 501 can supply reactive power to the AC grid 511 or extract reactive power from the AC grid 511 .

A method for cooling at least one electrical energy storage device of a converter is shown again in FIG. 6 with the aid of a flow chart.

Method step 602:

The coolant 70 pumped in the coolant circuit 72 by the modules 1_1 , . . . , 6_n of the converter 1

Method step 604:

The waste heat of the energy storage device 210 of the module 1_1 is absorbed by the coolant 70

Method step 606 (optional):

The waste heat of the switching elements 202 , 206 , 302 , 306 of the modules 1_1 , . . . , 6_n is absorbed by the coolant 70

Method step 608:

The waste heat is carried away to the heat exchanger 56 by means of the coolant 70

A converter having a plurality of modules and a method for cooling an energy storage device of the modules of the converter are described. In this case, the energy storage devices of the modules (eg capacitors of the modules) are cooled by means of a liquid coolant (liquid cooling). That is to say, the active cooling of the energy storage device takes place by means of a liquid coolant. Preferably, the cooling of the energy storage device takes place by means of the same liquid coolant, by means of which the switching elements of the modules are also cooled. Liquid cooling of energy storage devices yields a series of advantages:

- Energy storage devices (eg capacitors) with greater energy density/power density can be used.

- Convective spacing between electrical energy storage devices is not necessary or only minimally required. Thereby, the packing density of the energy storage device in the converter is increased.

- Significantly simplifies air conditioning of buildings in which converters are present (eg converter halls) (cost advantage).

-Increase the service life of the energy storage device.

Claims (11)

1. Converter (1) having a plurality of modules, each having at least two electronic switching elements (202, 206) and an electrical energy storage device (210), characterized in that the energy storage devices are liquid-cooled energy storage devices (210),

wherein the converter (1) has a cooling device (50) with a liquid coolant (70), and

wherein the cooling device (50) has a coolant pump (54) and a heat exchanger (56).

2. The current transformer of claim 1,

it is characterized in that the preparation method is characterized in that,

-the energy storage device (210) is thermally coupled with the coolant (70).

3. The current transformer of claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

the energy storage device (210) is thermally coupled to the coolant (70), wherein the energy storage device (210) is provided with a cooling body, and the cooling body is thermally coupled to the coolant (70).

4. The current transformer of claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

the electronic switching elements are liquid-cooled electronic switching elements (202, 206).

5. The current transformer of claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

the electronic switching elements (202, 206) are thermally coupled to the coolant (70).

6. The current transformer of claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

the electronic switching element (202, 206) is thermally coupled to the coolant (70), wherein the electronic switching element (202, 206) is provided with a cooling body, and the cooling body is thermally coupled to the coolant (70).

7. The current transformer of claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

the cooling device (50) has a coolant circuit (72) for cooling the energy storage device (210).

8. The current transformer of claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

the energy storage device is a capacitor (210).

9. The current transformer of claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

two of the electronic switching elements (202, 206) of the module are arranged in a half-bridge circuit, or

The modules each have two of the electronic switching elements (202, 206) and two further electronic switching elements (302, 306), wherein the two electronic switching elements (202, 206) and the two further electronic switching elements (302, 306) are arranged in a full bridge circuit.

10. A high voltage direct current transmission installation (401) with a converter (1) according to any one of claims 1 to 9.

11. A reactive power compensation installation (501) with a converter according to any of claims 1 to 9.

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